High resolution replicational banding techniques are employed to determine the relationship between chromosome structure (banding) and function (replication), as well as between chromosomes and specific types of neoplasia. Prophase and interphase techniques are used with synchronized lymphocytes and prematurely condensed chromosomes (PCC) respectively. A detailed replicational map of every human chromosome is constructed according to substages of the cell cycle S-phase; this map will be proposed as a reference point for standardization of high resolution banding nomenclature compatible with the criteria of the International System for Human Cytogenetic Nomenclature - ISCN (1978, 1980). The replicational chronology of the major components of the human genome such as G-, R-, and C-bands, Y and X-facultative heterochromatins is determined. The hypothesis that each chromomere represents a major unit of chromosomal replication is tested using high resolution BrdU incorporation with prophase and interphase chromosomal analysis. These new techniques are further applied in cancer-related cytogenetic phenomena. We intend to categorize transformed (leukemic) cells according to disorders in patterns of chromosomal replication and/or inactivation, with the purpose of identifying subgroups of acute lymphocytic leukemias which may have therapeutic and prognostic significance. Two other cytogenetic phenomena exclusively associated with malignancy are studied, i.e., double minute chromosomes (DMC) and homogeneously staining regions (HSR). Their function and origin are largely unknown, as are the laws that determine the size, number and mitotic segregational behavior of DMC. By applying BrdU incorporation and high resolution replicational banding, we intend to answer some of these questions. Different HSR-containing cell lines are studied, and the HSR characterized by their replicational behavior, presence or absence of internal regions of lateral asymmetry, and chromosomal location. The suggested interrelationship between HSR and DMC will be tested cytologically.